Factors associated with early catheterization in patients randomized to the conservative strategy in the ISCHEMIA Trial

Background

In the ISCHEMIA trial, individuals randomized to the conservative strategy (CON) could undergo coronary catheterization (cath) for suspicion of an endpoint event, persistent symptoms despite optimal medical therapy, or through protocol non-adherence. Understanding the reasons for cath in CON participants can aid in ISCHEMIA results interpretation.

Purpose

To describe the frequency of and factors associated with early cath in ISCHEMIA CON participants.

Methods

A prespecified, post-hoc analysis of the 2591 CON participants was performed with multivariable analyses to identify independent factors associated with cath within 6 months of randomization (“early cath”).

Results

Overall 8.7% (225/2591) of CON participants underwent an early cath: with 4.6% (119/2591) for a suspected endpoint, 1.6% (41/2591) for medical treatment failure, and 2.6% (67/2591) for protocol non-adherence; 67% of all these caths (151/225) occurred within the first 3 months from randomization. Independent factors associated with cath among CON participants included daily (HR=5.84, CI: 2.73–12.47, p<0.01) and weekly (HR=2.64, CI: 1.52–4.58, p<0.01) baseline angina vs no angina, severe (HR=2.02, CI: 1.03–3.95, p=0.04) and moderate baseline quality of life impairment vs no impairment (HR=2.03, CI: 1.24–3.33, p=0.01), randomization in Europe vs Asia (HR=1.83, CI: 1.15–2.9, p=0.01), with the proviso that all these characteristics were associated with cath occurring within the first 3 months of follow-up (very early cath), but not those between 3 and 6 months (proportional hazard assumption violation). Other factors independently associated with early cath were new or increasing angina pattern over 3 months pre-randomization (HR=1.79, CI: 1.33–2.39, p<0.0001) and increases in anti-anginal medication use during follow-up (HR=1.45, CI: 1.06–1.98, p=0.02). Baseline LDL-C <70mg/dL (HR=0.65 CI: 0.46–0.91, p=0.01) and a subsiding angina pattern during follow-up (HR=0.65, CI: 0.6–0.71, p<0.01) were independently associated with a reduced hazard of early cath. Neither ischemia severity nor extent of atherosclerosis on coronary imaging showed association with cath in CON participants at 6 months.

Conclusions

The rate of early cath in the ISCHEMIA CON strategy was low and driven mainly by a suspected endpoint event. Severe/moderate baseline angina and quality of life impairment were independently associated with very early cath. Chances of early cath were greater with worsening pre-randomization angina and need for additional antianginal medication, and less with well controlled LDL-C and decreasing angina pattern. The baseline severity of ischemia or extent of disease on coronary imaging were not related to early cath. These results give important insight into the coronary disease treatment trajectory in the conservative strategy of the ISCHEMIA trial, further inform real-life decision making and point to the efficacy of optimal medical therapy in reducing the need for cath.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health, National Heart Lunch and Blood Institute

Is there an inter-manufacturer difference in generic clopidogrel response?

Background

Differences in platelet aggregation response to generic clopidogrel by manufacturer has not been investigated.

Purpose

Compare rates of clopidogrel response among patients receiving medication produced by two different manufacturers after acute coronary syndrome and/or percutaneous coronary intervention.

Methods

This quality improvement project included 515 adult patients receiving clopidogrel for acute coronary syndrome or ischemic heart disease and referred for coronary angiography/percutaneous coronary intervention at a large, public hospital. The project was divided into two phases: 1. retrospective collection of baseline data; 2. two 12-week, prospective phases in which all clopidogrel in the hospital was restricted to a single manufacturer at a time. The primary outcome was clopidogrel response measured by platelet function testing defined as ADP response <40% on light transmission aggregometry between two manufacturer groups. Aspirin response defined as arachidonic acid response <20% was also measured.

Results

Of 515 total patients included in both phases (mean [SD] age, 64.5 [11.4] years; 351 [68.2%] men; 450 [87.4%] ACS), 52% were found to be clopidogrel responders based on results of platelet function testing (Table 1 – select variables). Among 135 patients in the prospective phase, there was a significantly lower proportion of patients who were clopidogrel responders in the Manufacturer 1 group compared to the Manufacturer 2 group (34.8% vs. 55.1%, p=0.03) (Table 2 – select variables). After adjustment for age, sex, BMI, aspirin response, therapeutic hypothermia, LHC indication, clopidogrel loading dose, time between loading dose and lab measurement, and manufacturer, aspirin response (OR [95% CI]: 0.96 [0.95–0.97], p<0.001) and manufacturer (OR [95% CI]: 2.45 [1.18–5.22], p=0.02) were associated with clopidogrel response.

Conclusions

In a large public hospital, we observed that pharmacodynamic response to clopidogrel varied by drug manufacturer. Further investigation and/or regulation is needed to minimize inter-manufacturer variability.

Funding Acknowledgement

Type of funding sources: None.

Cardioprotection with beta-blockers: myths, facts and Pascal's wager

Beta-blockers were documented to reduce reinfarction rate more than 3 decades ago and subsequently touted as being cardioprotective for a broad spectrum of cardiovascular indications such as hypertension, diabetes, angina, atrial fibrillation as well as perioperatively in patients undergoing surgery. However, despite lowering blood pressure, beta-blockers have never shown to reduce morbidity and mortality in uncomplicated hypertension. Also, beta-blockers do not prevent heart failure in hypertension any better than any other antihypertensive drug class. Beta-blockers have been shown to increase the risk on new onset diabetes. When compared with nondiuretic antihypertensive drugs, beta-blockers increase all-cause mortality by 8% and stroke by 30% in patients with new onset diabetes. Beta-blockers are useful for rate control in patients with chronic atrial fibrillation but do not help restore sinus rhythm or have antifibrillatory effects in the atria. Beta-blockers provide symptomatic relief in patients with chronic stable angina but do not reduce the risk of myocardial infarction. Adverse effects of beta-blockers are common including fatigue, dizziness, depression and sexual dysfunction. However, beta-blockers remain a cornerstone in the management of patients having suffered a myocardial infarction and for patients with heart failure. Thus, recent evidence argues against universal cardioprotective properties of beta-blockers but attest to their usefulness for specific cardiovascular indications.

Stress echocardiography: risk stratification, prognosis, patient outcomes and cost-effectiveness

The utilization of stress echocardiography has undergone considerable expansion and evolution over the past three decades. Although stress echocardiography was first conceived as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease (CAD), its prognostic value is now well established. Thus, identification of patients at risk for future cardiac events has become a primary objective in the noninvasive evaluation of patients with chest pain syndromes and among patients with known CAD. In particular, the ability of stress echocardiography to identify patients at low (<1%), intermediate (1-5%) or high (>5%) risk for future cardiac events is essential to patient management decisions. Moreover, previous studies have conclusively demonstrated the incremental prognostic value of stress echocardiography over clinical and treadmill exercise data, in predicting future cardiac events. This review addresses the current role and summarizes current literature with respect to the use of stress echocardiography in determining patient risk for cardiac events and the cost-effective integration of such information into patient management decisions.

A review of stroke in patients with hypertension and coronary artery disease: Focus on calcium channel blockers

Stroke is a major cause of morbidity and mortality worldwide. Hypertension is one of the most important risk factors for stroke - increasing the risk significantly. The presence and severity of coronary artery disease (CAD), which often coexists with hypertension, also predicts an increased risk of stroke. Lowering blood pressure (BP) to target in patients with hypertension can significantly reduce the incidence of fatal and non-fatal stroke. Effective BP control is even more important in CAD patients who are at greater risk of stroke. Data regarding the effects of antihypertensive therapy on stroke in patients with angina or CAD are limited and have been variable. To date, BP management strategies in patients with CAD have relied on small subsets of data based on high-risk hypertensive patients. Results with calcium channel blockers (CCBs) have been more positive than those with other classes of antihypertensive agents. Findings from the ACTION trial have provided a significant insight into the benefits of CCBs in patients with CAD and hypertension. Nifedipine gastrointestinal therapeutic system (GITS), in addition to best practice therapy for stable angina pectoris, contributes to a significant reduction in the risk of stroke in patients with CAD and hypertension who are at high risk and require effective BP control. Moreover, the incidence of stroke is significantly related to baseline BP, which may be an important factor to consider when deciding on treatment strategies in high-risk patients with CAD.

A mechanism for testosterone modulation of alpha-1 adrenergic receptor expression in the DDT1 MF-2 smooth muscle myocyte

Previous reports have confirmed that steroid hormones modulate the expression of adrenergic receptors on the surface of smooth muscle myocytes. The present study was undertaken to evaluate the mechanism by which testosterone modulates alpha-1 adrenergic receptor expression in the DDT1 MF-2 transformed smooth muscle cell. Utilizing 3H-prazosin radioligand binding studies, alpha-1 adrenergic receptors were noted to increase more than 2 fold in response to incubation with 10(-8)M testosterone for 96 hours. Dihydrotestosterone similarly stimulated a significant increase in alpha-1 receptors; whereas, estradiol and hydrocortisone appeared to suppress the expression of this receptor in DDT myocytes. The testosterone effect was dose related with a maximal response observed in response to 10(-7)M testosterone at both 48 and 96 hours. Kinetic experiments utilizing 10(-8)M testosterone demonstrated a peak effect on alpha-1 receptor expression at 96 hours, and maintenance of the effect for at least 168 hours (7 days). The testosterone effect was completely prevented at both 48 and 96 hours by inhibition of transcription with actinomycin-D, or inhibition of translation with cycloheximide. Consistent with the receptor binding studies, RNA blotting studies have demonstrated maximal alpha-1 receptor mRNA levels at 48-96 hours of testosterone stimulation. In conclusion, these in vitro experiments have confirmed the physiologic concentrations of testosterone stimulate the increased expression of alpha-1 receptors in the DDT1 MF-2 myocyte after a delay of 48-96 hours; and that this effect appears to be mediated by transcription, translation, and synthesis of new proteins in these genital tract myocytes.

Alpha-1, alpha-2, and beta adrenergic signal transduction in cultured uterine myocytes

The following studies were undertaken to develop a cultured uterine myocyte model which would allow further clarification of the adrenergic signal transduction mechanisms utilized by these myocytes. After mechanical removal of the endometrium, rabbit uterine myocytes were isolated by an overnight enzymatic disaggregation using collagenase and DNase I. The isolated myocytes were maintained in culture in 75-cm2 flasks containing Waymouth's MB 751/1 medium-10% fetal bovine serum along with 10(-8) M estradiol, penicillin, streptomycin, and Fungizone. The phase contrast and electron micrographic appearance of these cells was consistent with that previously reported for smooth muscle myocytes in culture. Immunocytochemical studies utilizing monoclonal anti-alpha-smooth muscle actin antibodies confirmed the presence of smooth muscle actin in these cultured myocytes. Western blot studies similarly confirmed the presence of alpha-smooth muscle actin in rabbit myometrial tissue and the cultured myocytes, both the primary and F1 generation. After prelabeling the myocytes with [3H]inositol, adrenergic stimulation experiments demonstrated alpha-1 receptor mediated stimulation of inositol phosphates. Beta receptor stimulation experiments confirmed cAMP production in these cultured myocytes, and the ability of clonidine, an alpha-2 agonist, to inhibit forskolin stimulated cAMP production confirmed the presence of functional alpha-2 adrenergic receptors in these myocytes. In conclusion, these cultured rabbit uterine myocytes have provided an in vitro model which can be utilized to further clarify the adrenergic receptor signal transduction mechanisms in genital tract smooth muscle.

Adrenergic stimulation of inositol-phosphate production in a genital tract smooth muscle cell line

Catecholamines are important in the modulation of smooth muscle contractile activity; this study was undertaken to evaluate adrenoceptor stimulation of intracellular inositol-phosphate production in a genital tract smooth muscle myocyte. DDT1 MF-2 smooth muscle myocytes, derived from a hamster ductus deferens leiomyosarcoma, were loaded with 3H-inositol, incubated in 10 mM LiCl, then stimulated with adrenergic agonists with and without antagonists. Subsequently, the inositol phosphates were isolated by anion-exchange chromatography. In the presence of norepinephrine (NE), inositol trisphosphate (IP3) was produced by 30 s and peaked at 2 min; inositol 1-phosphate was also apparent by 30 s, and continued to increase over 15 min. Clonidine (an alpha-2 agonist), isoproterenol, and NE in the presence of phentolamine or prazosin (an alpha-1 antagonist) failed to increase IP3. In contrast, NE in the presence of yohimbine (an alpha-2 antagonist) or propranolol stimulated IP3 production to levels comparable to that stimulated by NE alone. These studies provide evidence that inositol phosphate production is involved in alpha-1 adrenergic signal transduction in DDT1 MF-2 myocyte.

Genetic control of C6 polymorphism and C6 deficiency in rabbits

The genetic control of the sixth component of complement (C6) in rabbits has been studied by quantitation of C6 functional and antigenic levels and identification of polymorphism by isoelectric focusing (IEF) in gels. Patterns of inheritance of C6 variants in families carrying a silent gene for C6 were examined, and it was found that 3 common plasma phenotypic variants, C6 A, C6 B, and C6 QO were under the genetic control of allelic genes, C6*A, C6*B, and C6*QO. In IEF patterns, C6 A could be identified by its isoelectric point that was slightly more acidic than that of C6 B. C6 QO was undetectable because it lacked functional and antigenic activity. The C6*A/C6*B genotype displayed a mixed IEF pattern with bands characteristic of both C6 A and C6 B. Functional and antigenic levels of C6 that were found in heterozygous C6*A/C6*QO and C6*B/C6*QO rabbits were approximately one-half of the C6 levels found in the corresponding homozygous animals. The phenotypic variation closely resembles that previously observed in humans and rhesus monkeys, as well as preliminary data in rabbits. The patterns of inheritance indicated that the two common C6 structural genes and the deficiency gene were allelic variants at the same genetic locus.

Genetic control of C6 polymorphism and C6 deficiency in rabbits

The genetic control of the sixth component of complement (C6) in rabbits has been studied by quantitation of C6 functional and antigenic levels and identification of polymorphism by isoelectric focusing (IEF) in gels. Patterns of inheritance of C6 variants in families carrying a silent gene for C6 were examined, and it was found that 3 common plasma phenotypic variants, C6 A, C6 B, and C6 QO were under the genetic control of allelic genes, C6*A, C6*B, and C6*QO. In IEF patterns, C6 A could be identified by its isoelectric point that was slightly more acidic than that of C6 B. C6 QO was undetectable because it lacked functional and antigenic activity. The C6*A/C6*B genotype displayed a mixed IEF pattern with bands characteristic of both C6 A and C6 B. Functional and antigenic levels of C6 that were found in heterozygous C6*A/C6*QO and C6*B/C6*QO rabbits were approximately one-half of the C6 levels found in the corresponding homozygous animals. The phenotypic variation closely resembles that previously observed in humans and rhesus monkeys, as well as preliminary data in rabbits. The patterns of inheritance indicated that the two common C6 structural genes and the deficiency gene were allelic variants at the same genetic locus.

Functional and biochemical properties of the early classical complement system of mice

Mouse serum and EDTA plasma were subjected to low ionicity precipitation, gel filtration, and ion exchange chromatography in an attempt to purify C1, C4, and C2 to functional and chemical homogeneity. In marked contrast to human and guinea pig components, those of the mouse could not be separated by these techniques. Except for partial separation of C1 from C4 and C2 on DE-52 cellulose columuns with EDTA in the eluting buffers, there was no separation of those three components on ion exchange chromatographic columns. Sephadex G-200 gel filtration columns, or with precipitation of euglobulins from serum or plasma. Generation of EAC142 by incubation of EA in whole serum followed first order kinetics when mouse serum was used and second (or greater) order kinetics when human or guinea pig sera were used. Generation of EAC142 by incubation of EA in whole mouse serum followed by incubation in EDTA containing buffers resulted in rapid loss of all three activities from the cell. These experiments indicated that there were significant differences between the early classical C system of mice and those of human and guinea pig. In addition, they indicated that under a variety of in vitro conditions, murine C1, C4, and C2 behaved biochemically and functionally as a unit. The reasons for the major differences in behavior of the murine C components with not become clear until methods to stabilize their function are found so that they can survive multiple purification steps.